About the Rome IV Criteria for Functional Defecation Disorders
The only Rome IV diagnosis in this chapter that requires objective testing rather than symptoms alone. Two things must be true. First, the patient must satisfy the criteria for functional constipation and/or for irritable bowel syndrome with constipation — this is a diagnosis layered on top of another, not an alternative to it. Second, there must be evidence of impaired evacuation on at least two of three tests: an abnormal balloon expulsion test, abnormal anorectal manometry or anal surface EMG, and abnormal rectal evacuation on imaging. Meeting both then subclassifies into inadequate defecatory propulsion or dyssynergic defecation depending on whether the propulsive force is insufficient or the pelvic floor fails to relax.
Formula
Functional defecation disorder =
(meets functional constipation criteria OR meets IBS-C criteria)
AND ≥ 2 of 3 abnormal:
• balloon expulsion test
• anorectal manometry or anal surface EMG
• rectal evacuation imaging
Subtype:
inadequate propulsive forces → F3a inadequate defecatory propulsion
inappropriate contraction or < 20% relaxation of
basal resting sphincter pressure, with adequate
propulsive forces → F3b dyssynergic defecation- Two of three tests
- Not one. Rome IV requires corroboration because each individual test has meaningful false-positive and false-negative rates, particularly in the artificial setting of a laboratory.
- 20% relaxation
- The manometric threshold in dyssynergic defecation — less than 20% relaxation of basal resting sphincter pressure counts as abnormal, alongside frank paradoxical contraction.
- Adequate propulsive forces
- The feature that assigns a patient to dyssynergia rather than inadequate propulsion. Where propulsion is insufficient, the diagnosis is F3a regardless of what the sphincter does.
- This is the only Rome IV disorder in the anorectal chapter that requires objective testing — the rest are symptom-defined.
- The underlying diagnosis is a prerequisite, not an alternative: functional constipation or IBS-C must be met first.
- The 'two of three' rule exists because attempting defecation on a laboratory couch is unnatural and produces abnormal results in some healthy people.
- Straining, incomplete evacuation and digitation are what prompt testing; they are not themselves diagnostic criteria.
Interpreting the result
A positive result should redirect treatment rather than add to it. Biofeedback is the intervention with randomised evidence of benefit — it retrains the coordination of abdominal push and pelvic floor relaxation, and trials have shown it superior to laxatives, to sham feedback and to diazepam in dyssynergic defecation, with durable effect. It is not a course of exercises to do unsupervised; the benefit comes from instrumented feedback with a trained therapist, which is why access to a service matters. Laxatives may still be needed for stool consistency but should not be escalated in the expectation of resolving the outlet problem. Where testing is equivocal — one abnormal test out of three — the diagnosis is not met, and it is reasonable either to repeat testing or to trial biofeedback pragmatically in a patient whose symptoms fit strongly, while remaining clear that the criteria have not been satisfied. Where evacuation is impaired and there is also incontinence, treat the evacuation disorder first, since chronic impaction with overflow frequently resolves when the outlet problem is addressed.
| Score | Band | What it means | Action |
|---|---|---|---|
| F3a — Inadequate defecatory propulsion | Insufficient propulsive force | Underlying constipation criteria met plus 2 of 3 abnormal tests, with inadequate propulsion | Biofeedback with emphasis on generating effective abdominal propulsive pressure |
| F3b — Dyssynergic defecation | Adequate push, outlet fails to open | Inappropriate pelvic floor contraction or < 20% relaxation of basal resting sphincter pressure, with adequate propulsion | Biofeedback with emphasis on pelvic floor relaxation — randomised evidence of superiority over laxatives |
| Criteria not met | Threshold not reached | Underlying criteria not met, or fewer than two abnormal tests | Manage as functional constipation or IBS-C; consider repeat testing if symptoms strongly suggest an outlet problem |
What the Functional Defecation Disorders needs (6 inputs)
- Patient meets criteria for functional constipation and/or IBS with constipation
- Mandatory. Rome IV builds this diagnosis on top of an existing one — a patient who does not meet either underlying set of criteria cannot have a functional defecation disorder.
- Abnormal balloon expulsion test
- One of the three objective tests. Inability to expel a filled balloon within a defined time is the simplest and most accessible screen for impaired evacuation.
- Abnormal anorectal manometry or anal surface EMG
- Demonstrates the pattern during attempted defecation — insufficient propulsive pressure, or failure of anal relaxation or paradoxical contraction.
- Abnormal rectal evacuation on imaging
- Barium or MR defaecography showing impaired evacuation of rectal contents.
- Subclassification — propulsive force
- Inadequate defecatory propulsion (F3a) is defined by insufficient propulsive forces, with or without inappropriate anal contraction or inadequate relaxation.
- Subclassification — pelvic floor behaviour
- Dyssynergic defecation (F3b) is defined by inappropriate contraction of the pelvic floor, or by less than 20% relaxation of basal resting sphincter pressure, with adequate propulsive forces.
What it returns
- Whether the diagnostic threshold is met
- Underlying functional constipation or IBS-C, plus two or more abnormal tests of the three.
- Subtype
- Inadequate defecatory propulsion or dyssynergic defecation — distinguished by whether propulsive force is adequate.
- Whether biofeedback is indicated
- Both subtypes are biofeedback candidates, though the retraining emphasis differs.
How it is calculated
Normal defecation requires two things to happen at once: the abdominal muscles and diaphragm generate propulsive pressure, and the pelvic floor and anal sphincter relax to let stool pass. A functional defecation disorder is a failure of that coordination, and Rome IV separates the two ways it fails. In inadequate defecatory propulsion the push is insufficient, whatever the sphincter does. In dyssynergic defecation the push is adequate but the outlet does not open — the pelvic floor contracts paradoxically or relaxes by less than 20% of basal resting pressure. Either way the result is a functional obstruction that behaves nothing like slow transit, which is why laxatives disappoint. The insistence on two abnormal tests reflects a practical problem: defecating on demand, on a couch, with a catheter in place, is not a natural act, and a proportion of asymptomatic people produce abnormal results under those conditions. Requiring corroboration across two modalities reduces the chance of labelling a testing artefact as disease.
Facts & figures
| Test | What it shows | Practical notes |
|---|---|---|
| Balloon expulsion | Whether a filled balloon can be expelled in a defined time | Simplest and most accessible; good screening test but not sufficient alone |
| Anorectal manometry / anal surface EMG | Propulsive pressure and whether the sphincter relaxes on attempted defecation | Provides the < 20% relaxation threshold and separates the two subtypes |
| Rectal evacuation imaging | Whether rectal contents actually leave | Barium or MR defaecography; also identifies structural contributors such as rectocele or intussusception |
Two of the three must be abnormal. No single test is sufficient, because attempted defecation in a laboratory setting produces abnormal results in some healthy people.
| Feature | Inadequate propulsion (F3a) | Dyssynergic defecation (F3b) |
|---|---|---|
| Propulsive force | Insufficient | Adequate |
| Sphincter behaviour | May or may not contract inappropriately | Inappropriate contraction, or < 20% relaxation of basal resting pressure |
| Biofeedback emphasis | Generating effective abdominal push | Relaxing the pelvic floor during push |
| Underlying diagnosis required | Functional constipation and/or IBS-C | Functional constipation and/or IBS-C |
Adequacy of propulsive force is the deciding feature — where it is insufficient, the diagnosis is F3a regardless of sphincter behaviour.
Evidence
Derivation — Rome Foundation, anorectal disorders committee
2016Consensus criteria from the Rome IV anorectal disorders committee, published in Gastroenterology in 2016.
Rome IV retained the requirement for objective testing and strengthened it to two of three abnormal tests, reflecting the recognised false-positive rate of any single test performed in a laboratory setting.
Randomised trial — biofeedback versus laxatives
2006Randomised trial of biofeedback compared with polyethylene glycol in patients with dyssynergic defecation, reported by Chiarioni and colleagues in 2006.
Biofeedback was substantially superior to laxative therapy, with the advantage sustained at long-term follow-up — the core evidence for treating this group differently from other constipated patients.
Randomised trial — biofeedback versus sham and diazepam
2007Randomised controlled trial of manometric biofeedback against sham feedback and against diazepam in dyssynergic defecation, reported by Rao and colleagues in 2007.
Biofeedback outperformed both comparators, establishing that the benefit is not attributable to attention or to non-specific muscle relaxation.
Guideline adoption — ACG 2021
2021ACG clinical guideline on the management of benign anorectal disorders.
Recommends anorectal testing in constipated patients not responding to conservative therapy, and biofeedback as the treatment of choice where a defecation disorder is confirmed.
How it compares
Functional Defecation Disorders vs Functional constipation
One is the prerequisite for the other — and the reason to test is that the treatments diverge completely.
Functional constipation is symptom-defined and needs no testing. A functional defecation disorder requires those criteria to be met and then adds objective evidence of impaired evacuation on two of three tests. The clinical importance of separating them is that the treatments are different: functional constipation without an outlet problem responds to laxatives and dietary measures, while a defecation disorder responds to biofeedback and continues to fail escalating laxatives. A patient labelled refractory after several laxative failures should be tested rather than given a fourth agent.
Functional Defecation Disorders vs Rome IV IBS
IBS with constipation is an equally valid entry point — the defecation disorder can sit on top of either.
Rome IV explicitly permits the underlying diagnosis to be functional constipation or IBS with constipation, recognising that the two overlap heavily and that the presence of pain does not exclude an outlet problem. A patient with IBS-C who strains, digitates and fails laxatives deserves anorectal testing just as much as one labelled with functional constipation. Missing this is a common route to prolonged unsuccessful treatment, because the IBS label tends to close down further physiological assessment.
Functional Defecation Disorders vs Faecal incontinence
Opposite symptoms that frequently coexist — and the evacuation disorder should be treated first.
Impaired evacuation leads to chronic retention, and retention leads to leakage of liquid stool around impacted material. A patient can therefore meet criteria for both, and treating the incontinence with antidiarrhoeals makes matters worse. Both are assessed with anorectal manometry and both are treated with biofeedback, but the retraining targets differ, and resolving the outlet obstruction commonly resolves the leakage without any separate intervention.
Pearls & pitfalls
- This diagnosis sits on top of another — functional constipation or IBS-C must be met first, not instead.
- Two of three tests must be abnormal. A single abnormal balloon expulsion does not make the diagnosis.
- Straining, incomplete evacuation, splinting and digitation are the reason to test, not the criteria themselves.
- Laxatives do not fix an outlet problem. Escalating them in a patient with dyssynergia produces urgency without resolution.
- Biofeedback is instrumented retraining with a therapist, not unsupervised exercises — the evidence applies to the former.
- Adequacy of propulsive force is what separates the subtypes; where it is insufficient, the diagnosis is F3a whatever the sphincter does.
- Less than 20% relaxation of basal resting sphincter pressure counts as abnormal, alongside frank paradoxical contraction.
- A meaningful proportion of asymptomatic people fail single tests, which is exactly why corroboration is required.
- Where evacuation disorder and incontinence coexist, treat the evacuation problem first — overflow often resolves with it.
- Defaecography can also reveal rectocele or intussusception, which changes management independently of the Rome criteria.
Critical actions
- Confirm the patient meets functional constipation or IBS-C criteria before pursuing this diagnosis.
- Ask specifically about straining, sensation of incomplete evacuation, and the need to splint the perineum or digitate.
- Perform a digital rectal examination and observe the response to a simulated push — paradoxical contraction is often detectable at the bedside.
- Refer for anorectal physiology in constipated patients not responding to conservative measures rather than escalating laxatives indefinitely.
- Obtain at least two of the three tests, since one abnormal result does not meet the criteria.
- Record the subtype, since the biofeedback emphasis differs between inadequate propulsion and dyssynergia.
- Refer to a service that provides instrumented biofeedback with a trained therapist.
- Continue attention to stool consistency alongside biofeedback rather than stopping laxatives abruptly.
- Reconsider structural contributors on imaging — rectocele, intussusception — which may need separate management.
Why this score exists
The 'two of three' rule is the interesting decision here, and it is an admission against interest. Rome IV could have accepted a single abnormal test, which would have made the diagnosis far easier to reach and would have expanded the group offered an effective treatment. It did not, because the committee knew what the tests actually measure: a person asked to defecate on a couch, in a clinic, with a catheter in place and someone watching, is not doing the thing the test claims to assess. A meaningful proportion of asymptomatic volunteers fail balloon expulsion or show paradoxical contraction under those conditions. Requiring two independent modalities to agree is a way of demanding that the abnormality survive a change of setting and technique. It makes the criteria harder to satisfy and the diagnosis more trustworthy — which is the right trade when the alternative is committing patients to a course of instrumented retraining for an artefact.
About the creator
First author, Rome IV anorectal disorders committee; led the randomised biofeedback trial
Both chaired the criteria committee and produced much of the trial evidence underpinning biofeedback in dyssynergic defecation.
Co-author; lead author of the biofeedback versus laxative trial
His 2006 trial established biofeedback as superior to laxatives in this group.
Co-author; anorectal physiology
Contributed substantially to the physiological testing standards the criteria depend on.
Limitations
- Requires physiological testing that is not available in every centre, which limits where the diagnosis can be made at all.
- Each individual test has appreciable false-positive rates in asymptomatic people, which the two-of-three rule mitigates but does not eliminate.
- Attempting defecation in a laboratory setting is unnatural and may not reflect what happens at home.
- Patients with one abnormal test and strongly suggestive symptoms fall outside the criteria despite often responding to biofeedback.
- Manometric normal ranges vary between systems and protocols, so thresholds are not perfectly transferable.
- The criteria do not address structural findings such as rectocele or intussusception, which may coexist and need separate management.
- Consensus-derived, with no measured sensitivity or specificity against a clinical outcome standard.
- Access to instrumented biofeedback with a trained therapist is the practical limiting factor even when the diagnosis is made correctly.
If you are the patient
Opening the bowels normally needs two things to happen together: pushing down with the tummy muscles, and letting the muscles around the back passage relax so stool can pass. In some people that coordination goes wrong — either the push is not strong enough, or the muscles tighten instead of relaxing. The result feels like constipation, but it is really a problem at the exit rather than in the bowel itself, and that matters because laxatives do not fix it. Common experiences include straining a lot, feeling that you have not finished even after going, and sometimes needing to press around the area to help. To confirm it, a specialist does tests measuring the pressures in the back passage and checking whether you can push out a small balloon. Two tests need to agree before the diagnosis is made — deliberately, because doing this on a clinic couch is not natural and one odd result on its own is not reliable enough. The treatment that works is biofeedback: sessions with a therapist using sensors that show you what your muscles are doing, so you can learn to push and relax at the same time. It sounds simple but it works well, and studies have shown it beats laxatives clearly in this group. It is not the same as doing pelvic floor exercises at home — the feedback from the sensors is what makes the difference.
Frequently asked questions
What are the Rome IV criteria for functional defecation disorders?#
The patient must first meet criteria for functional constipation and/or IBS with constipation, and must then show evidence of impaired evacuation on at least two of three tests: balloon expulsion, anorectal manometry or anal surface EMG, and rectal evacuation imaging. Meeting both parts allows subclassification into inadequate defecatory propulsion or dyssynergic defecation.
Why are two abnormal tests required rather than one?#
Because attempting to defecate on a clinic couch with a catheter in place is not a natural act, and a meaningful proportion of asymptomatic people produce abnormal results under those conditions. Requiring two independent modalities to agree means the abnormality has survived a change of setting and technique, which makes the diagnosis considerably more trustworthy.
What is the difference between inadequate propulsion and dyssynergic defecation?#
Whether the push is adequate. In inadequate defecatory propulsion the propulsive force is insufficient, with or without abnormal sphincter behaviour. In dyssynergic defecation the propulsive force is adequate but the outlet fails to open — the pelvic floor contracts inappropriately or relaxes by less than 20% of basal resting sphincter pressure.
Can a patient with IBS have a functional defecation disorder?#
Yes — Rome IV explicitly allows IBS with constipation as the underlying diagnosis alongside functional constipation. A patient with IBS-C who strains, digitates and fails laxatives warrants anorectal testing. Missing this is a common cause of prolonged unsuccessful treatment, because the IBS label often stops further physiological assessment.
What treatment works?#
Biofeedback. Randomised trials have shown it superior to polyethylene glycol, to sham feedback and to diazepam in dyssynergic defecation, with durable benefit. It is instrumented retraining conducted with a therapist rather than unsupervised exercises, and the evidence applies specifically to the supervised form.
Why do laxatives not work?#
Because the problem is at the outlet, not in transit. Adding osmotic or stimulant laxatives to a functional obstruction increases urgency and discomfort without addressing the coordination failure that prevents evacuation. Laxatives may still be useful for stool consistency, but escalating them in the expectation of resolving the difficulty is what keeps these patients labelled refractory.
What symptoms should prompt testing?#
Straining, a sensation of incomplete evacuation, and the need to splint the perineum or digitate — particularly in a patient who has failed conservative measures. These are the reason to refer for anorectal physiology; they are not themselves diagnostic criteria, which is why the diagnosis cannot be made on history alone.
What if only one of the three tests is abnormal?#
The criteria are not met. It is reasonable either to repeat testing or, in a patient whose symptoms fit strongly, to trial biofeedback pragmatically — but the diagnosis should not be recorded as established. Being explicit about this matters when interpreting studies, since trial populations are defined by the full criteria.
References
Original / primary reference
Validation and treatment evidence
- Chiarioni G, Whitehead WE, Pezza V, Morelli A, Bassotti G. Biofeedback is superior to laxatives for normal transit constipation due to pelvic floor dyssynergia. Gastroenterology. 2006;130(3):657-664.
- Rao SSC, Seaton K, Miller M, et al. Randomized controlled trial of biofeedback, sham feedback, and standard therapy for dyssynergic defecation. Clin Gastroenterol Hepatol. 2007;5(3):331-338.